Research On Salinity Gradient Distribution Pattern And Ecological Mechanism Of Soil Bacteria In The Yellow River Delta

Explored the distribution pattern of soil bacterial community salinity gradient and understanded the ecological construction mechanism of soil bacterial community with high-throughput sequencing technology,bioinformatics,biostatistics and ecological theories and methods,which could provide important theoretical support for the utilization management and diversity protection of saline soil.In this study,a total of 19 plots were selected in three regions:the modern Yellow River Delta(Dongying,Shandong)and the ancient Yellow River Delta(Yancheng,Jiangsu).The physical and chemical properties,enzyme activity,and bacterial community composition of the soil were measured.Explored the distribution characteristics of soil bacterial communities and the dynamic changes of key species and their driving factors as the desalination process progresses.The conclusions obtained are as follow:(1)Soil quality of light-salt soils are generally higher than that of high-salt soils.With the decrease of salinization,the change of soil enzyme activity is gradually increasing,enzyme activity is expressed as light-salt soil > medium-salt soil > high-salt soil.Soil enzyme activity is closely related to soil physical and chemical properties,and the influence of conductivity on soil enzyme activity is the greatest,showing a significant negative correlation.(2)The soil salinity is different,and the composition of the bacterial community in the Yellow River Delta is also different.Proteobacteria is the dominant bacteria.Bacteroidetes and Firmicutes are relatively abundant in high-salt soils,while the abundance of Chloroflexi is higher in medium-salt soils,and Actinobacteria and Acidobacteria have relative advantages in light-salt soils.The relative abundance of Gammaproteobacteria ranks first on all gradients,showing the distribution characteristics of “ high-salt soil> medium-salt soil> light-salt soil ”.Stenotrophomonas is the dominant genus in the study area.The relative abundance ratio of Pseudomonas is high-salt soil> light-salt soil> medium-salt soil,and Bacteroides account for a relatively high proportion in high-salt soils,while Marinobacter has a relative advantage inhigh-salt and medium-salt soils,and Acinetobacter,Sphingomonas and Lysobacter have obvious advantages in light-salt soils.(3)Changes in salinity significantly affects the abundance and diversity of soil bacteria.The observed_species index,Shannon index,Simpson index,ACE index,Chao1 index and PD_whole_tree index decrease in different soils as soil salinity increases.Under different salinity gradients,the soil bacterial community structure is significantly different,but the soil bacterial community structure has greater similarity at the same salinity gradient;compared with the high-salt soil and medium-salt soil,the bacterial communities are more similar in light-salt soils.(4)Dominant bacteria also play a key role in the ecological network,affecting the stability of the bacterial network structure.Microorganisms have the fastest response speed in light-salt soils,and the microbial community is more prone to change.The positive correlation is absolutely dominant between microorganisms under various salinity gradients.As the natural succession collaborative niche increases and the positive correlation becomes stronger,bacterial communities respond to environmental changes by reducing competition and strengthening cooperation when interfered by the external environment.Environmental factors play a key role in the ecological network,which is consistent with the niche theory.(5)The analysis of the influencing factors of soil bacterial community in the Yellow River Delta shows that the four environmental factors of conductivity,temperature,alkali-decomposed nitrogen and total nitrogen are strongly correlated with the bacterial community structure,which plays a key role in the soil bacterial network of the Yellow River Delta.And it further indicates that the environment factors dominates the microbial community.Most of the bacteria affected by environmental factors come from the dominant groups in the soil of the Yellow River Delta,all of which belong to Stenotrophomonas.Stenotrophomonas belong to salt-tolerant bacteria,and many strains also have strong bioremediation function,which has important research value in soil remediation work.